Funding is requested to support our ongoing studies toward identification of molecular mechanisms mediating oncogenic effects of tobacco nitrosamines on respiratory cells and development of novel anti-cancer therapies using nicotinic acetylcholine receptor (nAChR) ligands. Preliminary studies revealed an anti-tumor potential of both canonical and non-canonical ligands of the nAChRs expressed on the cell membrane of respiratory cells. These receptors play a role in the malignant transformation of BEP2D cells caused by pharmacologic doses of the tobacco-derived carcinogenic nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The NNK-transformed and lung cancer cells are highly sensitive to apoptosis induced by the novel cholinergic peptide SLURP-1 (secreted mammalian Ly-6/urokinase plasminogen activator receptor [uPAR]-related protein). Integrating structural and functional information about SLURP-1 vs. NNK actions on respiratory cells will facilitate a better understanding of the physiologic mechanism of tumor surveillance in lungs, and may lead to the development of novel methods of prevention and treatments of tobacco-related lung cancer. We will test the following working hypotheses: 1) SLURP-1 can prevent NNK-dependent transformation of respiratory cells in vitro and in vivo; 2) cytoplasmic trapping of SLURP-1 results in altered expression of nAChRs on the plasma membrane of NNK-transformed BEP2D and lung cancer cells; 3) SLURP-1 acts as a competitive nAChR antagonist with the 17 nAChR subtype mediating most of SLURP-1 effects; and 4) SLURP-1 interferes with the receptor-mediated signaling downstream of the nAChR subtype(s) ligated by NNK in normal and malignant human respiratory cells. The Specific Aims will be to determine: 1) the role of SLURP-1 in the physiologic protection of respiratory cells from NNK carcinogenicity; 2) the molecular mechanism of increased sensitivity of malignant respiratory cells to the apoptosis induced by SLURP-1; 3) the nAChR subtype(s) mediating the pharmacologic activity of SLURP-1 and the mode of its action on the nAChRs expressed by respiratory cells; and 4) the signaling pathways downstream of the nAChRs ligated by SLURP-1 and NNK.